The subject matter of the present invention relates generally to dual alternating transverse feeding mechanisms including a set of first dogs and a set of second dogs for conveying lumber pieces, or flitches, cut from a log and having at least one flat surface and more commonly having opposed flat surfaces on their top and bottom faces, laterally on a supply conveyor after they pass through a light scanner to determine their optimum yield reference axis, from a start position to a feed position aligned with a feed conveyor for longitudinally conveying the lumber pieces through a lumber edger cutting device to cut the edges from such pieces to provide the optimum yield of boards. One embodiment of the present invention relates to such a feeding mechanism for a lumber edger in which the first and second dogs may be mounted for alternatively conveying successive lumber pieces from the start position to the feed position and for returning from the feed position to the start position on opposite sides of the next lumber pieces to enable faster and more efficient operation of the feeding mechanism. Such feeding mechanism may include actuating motors with rotatable output gears which are employed to pivot the dogs between a raised, or extended, position for engagement with the lumber pieces and a retracted position to enable return of the dogs from the feed position to the start position. Such actuating motor may be an electric motor which moves with the dog to which it is connected to provide a simple, compact and trouble-free actuating mechanism for pivoting the dogs.
The feeding mechanism of the present invention includes a pair of drive cylinders and guides for moving the first and second dogs which are mounted side-by-side to provide a compact and strong drive mechanism for moving lumber from the start position to the feed position. In addition, such drive mechanism may also employ an air stop cylinder which engages the lumber piece, or flitch, as it is conveyed toward the feed position by the dogs to engage and stop such piece at the feed position and thereby position the lumber piece in alignment with the feed conveyor in a faster and more accurate manner.
It has previously been proposed in U.S. Pat. No. 1,838,780 of Miller et al., issued Dec. 29, 1931, to provide an automatic feeding machine for feeding lumber to a resaw machine or edger by using alternating dogs which engage successive lumber pieces and are moved by an air cylinder to feed the pieces to the resaw machine when the dogs are in a raised position and which allows the dogs to return beneath the next lumber piece with the dogs in a retracted position. Unlike the lumber feeding mechanism of the present invention, this prior feeding mechanism employs an air cylinder whose piston rod is connected to a support for moving one of the dogs and is coupled by an external rack and pinion gear to the second dog for movement thereof in the opposite direction to the first. Unlike the feeding mechanism of the present invention, the dogs of the above-discussed Miller patent are each pivoted to a raised position by a spring until such dogs engage a stop and are pushed downward into a retracted position by a cam action when the dog is returned underneath the support table which pivots the dog against the force of the spring. The present invention employs an actuation motor having an output gear for pivoting the dogs between the raised, or extended, and retracted positions which avoids the use of spring actuated dogs. In addition, while the dogs of the Miller patent are moved to the feed position by an air cylinder, there is no air stop cylinder for engagement with the lumber pieces as they are moved toward the feed position for more accurate positioning in the manner of the present invention.
It has also been proposed in U.S. Pat. No. 4,462,443 of Allen, issued Jul. 31, 1984, to provide a positioning and feeding apparatus for a lumber edger including a pair of clamps which clamp the lumber piece between such clamps before it is fed to the edger and after the piece is scanned with a light scanner to determine a reference axis on the lumber piece for optimum yield of boards. The Allen patent also shows that the clamps are pivoted between a raised position to engage the lumber piece and a retracted position to enable them to pass beneath the lumber and surface of the conveyor by a tilt cylinder. Also a clamp motor is required to rotate a screw drive to move the clamps toward and away from one another. No such clamps, clamp screw motor and tilt cylinder are employed in the feeding mechanism of the present invention. Instead, a simple actuating motor with a rotating output gear is employed to pivot the dogs in the present feeding mechanism. In addition in one embodiment of the feeding mechanism of the present invention, the first and second sets of dogs are mounted alternately above and below the supply conveyor so that when the dogs are pivoted to the retracted position and moved from the feed position to the start position, they travel over opposite sides above and below the lumber piece rather than on the same side of the piece as in both the Allen patent and the Miller patent.
It is shown in U.S. Pat. Nos. 5,011,001 and 5,694,993 both of Cameron, issued Aug. 30, 1991 and Dec. 9, 1997 respectively, to provide an end-dog carriage for moving logs by engagement of the opposite ends of the logs with dogs which clamp the log and move it along a track by means of fluid cylinders. The dogs are pivoted by cylinders mounted on the dog carriages from a retracted position to an extended position and are not moved by actuating motors with a rotating output gear to cause such pivoting in the manner of the present invention.
In addition, U.S. Pat. No. 5,052,885 of Foster, issued Oct. 1, 1991, shows a dual overhead end-dogging system for clamping a log between two dogs which engage the opposite ends of the log and in which the dogs are pivoted from an extended position to a retracted position by a cylinder. However, the end-dog clamping systems of the Foster patent and the Cameron patents are not suitable for engagement with the edges of lumber pieces or flitches to feed them laterally on a supply conveyor to a feed conveyor which conveys the pieces longitudinally to a lumber edger in the manner of the present invention.
As shown in U.S. Pat. No. 4,462,443 of Allen, referred to previously, and in U.S. Pat. No. 4,803,371 of Durland, issued Feb. 7, 1989, it is old to scan lumber pieces with a light scanner to determine a reference axis before such pieces are conveyed to a lumber edger cutting means which cuts the pieces into boards of the proper size for optimum yield of boards.